Kosmos 428
Kosmos 428 ( meaning CoSMoS 428) was launched by the USSR on Jun 24 1971 and recovered Jul 6 1971. The ORBit was apogee/perigee/inclination 208 km, 271 km, and 51.8°, respectively. It was a military satellite on which X-ray astronomy experiments had been added.
Instrumentation
There was a CsI(Tl) scintillation spectrometer sensitive to hard X-rays > 30 keV, with a 1.9° x 17° field of view (FOV). The scintillator crystal was 80 mm in dia (effective area 23 cm2) and 20 mm thick. The spectrometer had a slit collimator, with both passive and active shielding. In addition, there was an X-ray telescope (XRT) which operated in the range 2-30 keV.
Scientific accomplishments
Though its mission was brief, it detected several X-ray sources which were correlated to already identified Uhuru point sources. Five of these discrete sources of hard X-rays were 3U1543-47, 3U1700-37, 3U1705-44, 3U1820-30, with one remaining unidentified. Many discrete hard X-ray sources were recorded by Kosmos 428, with the strongest ones concentrated toward the Milky Way galactic plane. About 75 such sources had a measured luminosity of about 1.5×1031 watts (1.5×1038 erg/s) in the 30–200 keV range.
In the soft X-ray range are detected sources 3U 1704-32 and GX 340+6. In the immediate vicinity of the galactic equator where many of the soft X-ray sources are concentrated, there are practically no hard X-ray sources. Soft X-rays were also detected from Kosmos HX No. 9 (3U 1700-37). This source produced hard X-rays above 30 keV but was found to be variable.